Vulcanization of halogenated rubbery polymers with hexahydrodiazines



VULCANTZA'HON F HALGGENATED RUBBERY POLYMERS WITH HEXAHYDRODIAZINES Leon S. Miuclrler, in, Metuchen, Delmer L. Cottle, Highland Paris, and Thendore Lemiszka, Roselle, N.J., assignors to Essa Research and Engineering Company, a corporation of Delaware No Drawing. Filed Apr. 22, 1959, Ser. No. 808,001

16 Claims. (Cl. 260-415) This invention relates to rubbery polymeric compositions which are halogenated copolymers of isoolefins and multiolefins and to the preparation and vulcanization of such compositions and more particularly to improved methods for curing halogenated butyl rubber at an accelerated rate with minor proportions of heterocyclic secondary diamines containing four carbon atoms and being of the class of hexahydrodiazines.

Copolymers of the above general type, especially where the copolymer contains about 85 to 99.5% (preferably about 95 to 99.5%) of a C to C isoolefin such as isobutylene with about 15 to 0.5% (preferably 5 to 0.5 Weight percent) of a multiolefin of about 4 to 14, preferably about 4 to 6 carbon atoms and having a Staudinger molecular weight of between about 20,000 and 300,000, are commonly referred to in patents and literature as butyl rubber or GR-I rubber (Government rubber isobutylene) and, for example, is referred to as butyl rubher in the textbook Synthetic Rubber, by G. S. Whitby. The preparation of butyl type rubber is described in US Patent 2,346,128 to Thomas et a1. as well as in technical literature. In general, the multiolefinic component of the rubber comprises a conjugated diolefin such as isoprene, butadiene, dimethyl butadiene, piperylene, etc. The reaction product of isobutylene and isoprene is preferred. Butyl rubber has a mole precent unsaturation of between about 0.5 and 15.0.

It is known that halogenated butyl-type rubbery copolymers may be vulcanized with Zinc oxide or acylic diamines or triamines. Such halogenated copolymers are produced by halogenating the butyl rubber in a manner which does not degrade the molecular weight thereof, but halogenated sufficiently to produce a rubbery product which, when vulcanized, retains its tensile strength upon heat aging. However, the vulcanization of halogenated butyl rubber by zinc oxide or acyclic diamines is relatively slow and often results in vulcanizates possessing only poor to fair dynamic properties as determined in Goodrich flexometer tests.

In accordance with the present invention, it has now been discovered that halogenated butyl rubber may be cured at an accelerated rate to produce vulcanizates exhibiting improvements in stress-strain properties such as improved tensile strength and extension modulus, as well as improved hysteresis and dynamic properties such as permanent set and dynamic drift by vulcanizing the halogenated butyl rubber in the absence of other curatives such as zinc oxide, acyclic diamines and triarnines or sulfur with minor proportions of hexahydrodiazines such as hexahydro-l,2 diazine, hexahydro 1,3 diazine and/or especially hexahydro-1,4-diazine (.e. piperazine).

In practicing the present invention, 100 parts by weight of halogenated butyl rubber are compounded in the absence of added sulfur, acyclic diarnines and zinc oxide, with about 0.05 to 15, advantageously about 0.2 to 8.0 and preferably about 0.5 to 3.0 parts by weight of at least one hexahydrodiazine with the optional addition of such conventional compounding agents as about 5 to 15.0,

2,984,642 Patented May 16, 196i preferably about 20 to parts by weight of a filler such as clays, carbon blacks, TiO diatomaceous earth, etc., antioxidants such as pheny beta-naphthylarnine, antitack agents such as stearic acid, resins, plasticizers, etc. The resulting compounded stock is then cured by heating the same for about 1 second to 5 days, advantageously for about 20 seconds to 5 hours and preferably for about 1 minute to 2 hours at a temperature level of about 50 to 450 F., advantageously about 70 to 400 F. and preferably about 200 to 375 F. to produce a vulcanizate having a combination of excellent tensile strength and extension modulus as well as low dynamic drift and permanent set.

In producing halogenated butyl rubber to be vulcanized in accordance with the present invention, unmodified, unvulcanized butyl rubber is carefully halogenated so as to contain about at least 0.5 weight percent (preferably at least about 1.0 weight percent) combined halogen but not more than about "X weight percent combined fluorine or chlorine or 3 X Weight percent combined bromine or iodine wherein:

and:

L=mo1e percent of the multiolefin in the polymer M =molecular weight of the isoolefin M =molecular weight of the multiolefin M =atomic weight of halogen Restated there should be at least about 0.5 weight percent of combined halogen in the polymer but not more than about one atom of fluorine or chlorine or 3 atoms of bromine or iodine combined in the polymer per molecule of multiolefin present therein: i.e., not more than about one atom of combined fluorine or chlorine or three atoms of combined bromine or iodine per double bond in the polymer.

Suitable halogenating agents which may be employed are gaseous chlorine, liquid bromine, hydrogen fluoride, iodine monochloride, alkali metal hypochlorites, sodium hypobromite, C to C tertiary alkyl hypochlorites or hypobromites, sulfur chlorides or bromides (particularly oxygenated sulfur chlorides or bromides), pyridinium chloride perchloride, N-bromosuccinimide, tri-bromophenol bromide, N-chloroacetamide, N,N-dimethyl-5,5 dichloro or dibromo hydantoin, and other common halogenating agents.

The halogenation is generally conducted at about 50 C. to about C., advantageously at about 0 to 65 C., preferably at about 20 to 50 C. (room temperature generally being satisfactory), depending upon the particular halogenation agent, for about one minute to several hours. An advantageous pressure range is from about 0.5 to 400 p.s.i.a.; atmospheric pressure being satis factory. The halogenation conditions are regulated to halogenate the rubbery copolymer to the extent above mentioned.

The halogenation may be accomplished in various ways. For instance, the solid copolymer may be halogenated per se. Another process comprises preparing a solution of the copolymer as above, in a suitable inert liquid organic solvent such as a C to C or preferably a C to C inert hydrocarbon or halogenated derivatives of saturated hydrocarbons, examples of which are hexane, heptane, naphtha, mineral spirits, cyclohexane, alkyl substituted cycloparaffins, benzene, chlorobenzene, chloroform, trichloroethane, carbon tetrachloride, mixtures thereof, etc., and adding thereto gaseous chlorine, liquid bromine, or other halogenating agent, which may optionally be in solution, such as dissolved in an inert hydrocarbon, an alkyl chloride, carbon tetrachloride, etc.

o The concentration of the butyl rubber in the solvent will depend upon the type of reactor, molecular weight halogenation agent, and amount of halogen combined in the copolymer being as follows:

Halogenated (Percent) Rubber Isoolefin (Percent) 1 Multlolefin (Percent) I Halogenatlon Agent Halogen in the Rubber 1 Isobutylene (98) Isoprene (2) 1.2 chlorine. Isobutylene (95) 2.5 chlorine. Isobutylene (94) 1.8 iodine. Isobutylene (92) Myrcenc (8.0) 1.6 chlor ne. 2-methyl-butene-1 (95) Isoprene C12 in Hexanc 1.5 chlorine. 3-methyl-butene-l (96)- Butadiene (4 Iodine Monochlor de 0.9 (11110. Isobutyleue (98) l-vinyl eyclohexene-3 (2) N-bromosuccinimide 0.5 brom ne. Butadiene (8) Gaseous Chlorine. 2.8 chlor ne. Isoprene do 6.6 chlor ne. Isobutylene (98)-.. N,N-dichloro-5,5- 1.1 chlorine.

dimethyl hydantoin. L do do Liquid Bromine 2.3 bromine.

1 N ore-(Percent) in all instances is percent by weight.

of the butyl rubber, etc. In general, the concentration of a butyl rubber having a viscosity average molecular weight of about 200,000 to about 1,500,000, if the solvent is a substantially inert hydrocarbon, will be between 1 and 30% by weight, preferably about 5 to If chlorine gas is employed to chlorinate such a rubbery solution, it may also be diluted with up to about 50 times its volume, preferably about 0.1 to 5.0 times its volume of an inert gas such as nitrogen, methane, ethane, carbon dioxide, etc.

The resulting halogenated butyl rubber polymer may be recovered in various manners. The polymer may be precipitated with acetone or any other known non-solvent for the butyl rubber anddried under about 1 to 760 millimeters or higher of mercury pressure absolute at about 0 to 180 C., preferably at about 50 to 150 C., e.g. 70 C.). Other methods of recovering the halogenated butyl rubber polymer from the hydrocarbon solution of the same are by conventional spray or drum drying techniques. Alternatively, the halogenated butyl rubber-containing solution may be injected into a vessel containing agitated water heated to a temperature sufficient to flash oil the hydrocarbon solvent and form an aqueous slurry of the halogenated butyl rubber. The halogenated butyl rubber may then be separated from this slurry by filtration, dried and recovered as a crumb or as a dense sheet or slab by conventional milling and/or extruding procedures. The halogenated copolymer formed advantageously has a viscosity average molecular weight between about 200,000 and 1,500,000 and a mole percent unsaturation of between about 0.5 to 15.0, preferably about 0.6 to 5.0.

In order to more fully illustrate the present invention, the following experimental data are given:

CHLORINATED BUTYL RUBBER A A copolymer of about 97% isobutylene and 3% isoprene having a viscisity average molecular weight of 320,000 was dissolved in hexane to form a 10% solution. To this polymer solution, a 20 weight percent (based on the polymer) of liquid sulfuryl chloride as the chlorinating agent was added and reacted for 30 minutes with the polymer at room temperature. The resulting chlorinated copolymer was preciptated with acetone, collected and redissolved in hexane three times and ultimately dried and analyzed and found to have a viscosity average molecular weight of 320,000 and to contain 1.4% chlorine based on the polymer. The physical characteristics of both zinc oxide and diamine-cured vulcanizates, containing this chlorinated interpolymer, were excellent.

HALOGENATED BUTYL RUBBERS B TO L Other examples of halogenated isoolefin-multiolefin copolymers which may be used are tabulated hereinafter, the amount of isoolefin and multiolefin in copolymer,

CHLORINATED BUTYL RUBBER M An additional run was made chlorinating a commercial butyl rubber dissolved in benzene. The butyl rubber had a Mooney viscosity at 212 F. for 8 minutes of 75, and a mole percent unsaturation of 1.6. The chlorination of a solution of the uncured butyl rubber was conducted in a 500-gallon glass-lined Pfaudler reactor equipped with an agitator, battle, submersed stainless steel sparger ring and a conduit leading into the ring.

Gaseous chlorine was continuously added to the butyl rubber solution over a period of /2 hour at a temperature level of 30 C. and under atmospheric pressure. The chlorine was added to the reactor through the conduit via the sparger ring. The chlorination was then terminated and the solution containing the chlorinated butyl rubber formed was agitated for an additional 20 minutes. The resulting solution of chlorinated butyl rubber was then water washed three times to remove dissolved hydrogen chloride.

The absolute amount of butyl rubber, benzene solvent and gaseous chlorine added, as well as the calculated percent of added chlorine based on polymer and resulting percent of chlorine combined in the polymer were as follows:

The resulting water-washed solution containing the stabilized, chlorinated butyl rubber M was then recovered by injecting the solution into an agitated aqueous slurry containing zinc stearate and a small amount of a non-ionic wetting agent of the aliphatic polyoxyethylene ether type (e.g., Sterox A] or Tergitol NPX) in an amount of 0.7 pound of the zinc stearate per pounds of chlorinated butyl rubber as a dispersing aid. The agitated solution was maintained at a temperature between about 190 and 210 F. (e.g., 200 F.) whereby to flash off the benzene solvent and form an aqueous slurry of the chlorinated butyl rubber in water. This slurry was then filtered and the chlorinated butyl rubber, which was in the form of a wet crumb, was placed in a Proctor and Schwartz tray drier maintained at F. (i.e., 82? C.) and dried for 12 hours. The crumb depth on the tray was about /2 inch. The crumb was then completely dried 100 parts by weight of chlorinated isobutylene-isoprene butyl rubber copolymer having a Mooney viscosity (212 F. for 8 minutes) of 65, a mole percent unsaturation of 1.3, a viscosity average molecular weight of 475,000 and a combined chlorine content of 1.1 weight percent were compounded with 50 parts by weight of HAF carbon black, 1.0 part by weight of stearic acid and 2.0 parts by The above data show that piperazine cures brominated butyl rubber more rapidly and into higher tensile strength materials than does zinc oxide.

Resort may be had to modifications and variations of the disclosed embodiments without departing from the weight of either an alicyclic diamine or triamine, or, in spirit of the invention or the scope of the appended accordance with the present invention, with 2.0 parts claims. by weight of the cyclic secondary diamine known as hexa- What is claimed is: hydro-1,4-diazine (i.e. piperazine). All compounded 1. A vulcanizable composition comprising a major stocks formed were then cured at 307 F. for 30 and 60 proportion of a rubbery halogenated copolymer of about minutes with the following physical inspections being 85 to 99.5 weight percent of a C to C isoolefin and noted: about to 0.5 weight percent of a C.; to C multiolefin N,N'-Di- Piperazine (l-meth- N,NDiiso-N,N-Dlisop,p'- Amine Compound of the yloctyl) octylhexaoctyl- Diethylenediamine- Iuvention) p-phenmethylene ethylenetriamiue diphenylylene diamine diamine methane diamine Tensile, cure (p.s.i.) 2, 050 400 735 950 2, 245 1,130 300 1,900 250 400 460 1, 645 540 380 800 740 590 395 635 2, 000 805 1,112 1, 385 2,190 1, 750 2, e00 380 560 075 2,150 985 300 055 590 550 305 500 0 Failed Failed Failed 6. 3 Failed 1. 7 Failed Failed Failed 16. 8 Failed 60 4s 45 4e 47 45 The above data show that, in accordance with the presand a vulcanizing amount of a hexahydrodiazine, said out invention, the cyclic secondary diamine, hexahydro- 30 copolymer containing at least 0.5 weight percent halogen. 1,4-diazine (i.e. piperazine) cures chlorinated butyl rub- 2. A composition according to claim 1 in which the ber more rapidly than other alicyclic diamines or trihalogenated copolymer is selected from the group conamines. The vulcanizates of the present invention also sisting of those containing at least 0.5 weight percent possess higher tensile strengths, moduli and hardness, chlorine but not more than about one atom of chlorine coupled with desirably lower values of dynamic drift and per double bond in the copolymer, those containing at permanent set. least about 0.5 weight percent bromine but not more Example II than about three combined atoms of bromine per double The same general procedure as in Example I was mind In the copPlymfir, and mlxmres repeated substituting 5 par-ts by weight of zinc oxide A QPQ P accordmg to 0131111 1 In which the for the two parts by weight of various alicyclic diamines hexahydmdlazme 1S 1 F 111 an amount of between and ,triaminos. Upon curing at for minutes about 0.05 and 15.0 welght percent based on halogenated or at 307 F. for 15 minutes the following physical incopolymer i Speofions were noted; 4. A composltron accordlng to claim 1 in Wl'LlCh the hexahydrodiazine is hexahydro-l,2-diazine. Zno Control Piperame Cure (of 5. A composition according to claim l in which the the Invention) hexahydrodiazme 1s hexahydro-1,3-d1az1ne.

6. A composition according to claim 1 in which the 300% Tensile Percent 300% Tensile Percent hexahydrodiazine is hexahydro-1,4-diazine. Mod. (p.s.1.) Elong. Mod. (p.s.1.) Elong. 7. A composition according to claim 1 which has been a vulcanized by heating the same for between about 1 SE23 3; 582,, 32? ggg igg 338 h3g2 fig second aild 5 days at a temperature level of between about 50 and 450 F. to produce a vulcamzate having a high tensile strength and low permanent set. The above data show that the piperazine cured vulcanizate of the present invention surpasses the zinc oxide composmon compnsmg a nibbery polymer cured vulcanizate as to both extension modulus and tenmg a vlscoslty average molecular weight of a least about sue strength 100,000 comprising atoms of hydrogen, carbon and a Exam 13 HI halogen selected from the group consisting of fluorine,

p chlorine, bromine, iodine and mixtures thereof, con- The Same general Procedure as 111 Example H was taining in its structure a major proportion of hydrorepeate? f that halogenated butyl rubber was carbon units derived by the polymerization of isoolefins a bromlPated lsobutyleQe'lsoPrene rubber f 0 containing about 4 to 7 carbon atoms and also containing mer havlng a Mooney Vlscoslty 2 for 8 a s sufiicient units in which a pair of carbon atoms is linked of 66, a mole P maturation of 3 9 by an olefinic double 'bond that the mole percent unsataverage molecular weight of 476,000, and a combined oration is between about 05 and 15; said polymer bmmme content of welght The n taining at least about 0.5 weight percent halogen but were as follows when cured at 250 F. for 5 and 15 mmnot more than about one combined atom of halogen Utes YesPecm/elyi per double bond in the polymer; said polymer being in composition with a vulcanizing amount of a hexahydro- Z110 Comm f fig g gfif diazine, said composition being free of sulfur, zinc oxide and alicychc amines. Tensile mom Tensile Elam 9. A composition according to claim 8 in which the g g sgggg g g 5:52:2 polymer contains chlorine.

.1. N p 10. A composltron according to cla1m 8 in which the ()medBMiu 345 705 2,415 235 Polymer Cured 15 Min 1,775 425 2,435 225 11. A composition according to claim 8 m WhlCh the hexahydrodiazine is present in an amount of between 7' about 0.2 and 8.0 weight percent based on the halogencontaining polymer.

12. A composition according to claim 8 in which the polymer is also in composition with about 5.0 to 150 parts by weight of a filler per 100 parts by weight of polymer.

13. A composition according to claim 8 which has been vulcanized for between about 15 minutes and 2 hours at a temperature level of between about 70 and 400 F. to produce a vulcanizate having a high tensile strength and low permanent set.

14. A process which comprises vulcanizing halogenated butyl rubber containing at least 0.5 weight percent halogen in the presence of about 0.05 to 15.0 weight 8 percent of a hexahydrodiazine at a temperature level of between about 70 and 400 F. until the resulting vulcanizate exhibits a tensile strength of at least about 1500 p.s.i. and a permanent set of below about 5%.

15. A process according to claim 14 in which the halogenated butyl rubber contains chlorine.

16. A process according to claim 14 in which the halogenated butyl rubber contains bromine.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A VULCANIZABLE COMPOSITION COMPRISING A MAJOR PROPORTION OF A RUBBERY HALOGENATED COPOLYMER OF ABOUT 85 TO 99.5 WEIGHT PERCENT OF A C4 TO C7 ISSOLEFIN AND ABOUT 15 TO 0.5 WEIGHT PERCENT OF A C4 TO C14 MULTIOLEFIN AND A VULCANIZING AMOUNT OF A HEXAHYDRODIAZINE, SAID COPOLYMER CONTAINING AT LEAST 0.5 WEIGHT PERCENT HALOGEN.
 8. A COMPOSITION COMPRISING A RUBBERY POLYMER HAVING A VISCOSITY AVERAGE MOLECULAR WEIGHT OF A LEAST ABOUT 100,000 COMPRISING ATOMS OF HYDROGEN, CARBON AND A HALOGEN SELECTED FROM THE GROUP CONSISTING OF FLUORINE, CHLORINE, BROMINE, IODINE AND MIXTURES THEREOF, CONTAINING IN ITS STRUCTURE A MAJOR PROPORTION OF HYDROCARBON UNITS DERIVED BY THE POLYMERIZATION OF ISOOLEFINS CONTAINING ABOUT 4 TO 7 CARBON ATOMS AND ALSO CONTAINING SUFFICIENT UNITS IN WHICH A PAIR OF CARBON ATOMS IS LINKED BY AN OLEFINIC DOUBLE BOND THAT THE MOLE PERCENT UNSATURATION IS BETWEEN ABOUT 0.5 AND 15, SAID POLYMER CONTAINING AT LEAST ABOUT 0.5 WEIGHT PERCENT HALOGEN BUT NOT MORE THAN ABOUT ONE COMBINED ATOM OF HALOGEN PER DOUBLE BOND IN THE POLYMER, SAID POLYMER BEING IN COMPOSITION WITH A VULCANIZING AMOUNT OF A HEXAHYDRODIAZINE, SAID COMPOSITION BEING FREE OF SULFUR, ZINC OXIDE AND ALICYCLIC AMINES.
 12. A COMPOSITION ACCORDING TO CLAIM 8 IN WHICH THE POLYMER IS ALSO IN COMPOSITION WITH ABOUT 5.0 TO 150 PARTS BY WEIGHT OF A FILLER PER 100 PARTS BY WEIGHT OF POLYMER. 